The present invention pertains to light transmission via single mode optical fiber and more particularly a transducer arrangement for interacting acoustic waves with light waves traveling in a single mode optic fiber.
The problem of effectively coupling information to an optical fiber and detecting the light transmitted through an optical fiber have long existed. Fiber optic tap connectors which provide this coupling are well-known in the art. Typically, such connectors have an element which pierces the fiber optic cable to deflect a portion of the light transmitted through the cable for detection and coupling to other devices. One such connector is shown in U.S. Pat. No. 4,741,584 issued on May 3, 1988 to E. Segerson and assigned to the same assignee as the present invention. However, piercing or cutting the optical fiber weakens the fiber and may produce a signal loss.
The above-mentioned problems exist for coupling to optical fiber which is already connected in-place between two points. Another arrangement for coupling to an inplace optical fiber includes the attachment of clamshell (glass) capillary halves having an outer transducer bonded about the outer surface of the glass clamshell. In this configuration, two semi-circular halves of a glass rod must be precisely cut longitudinally. Such cutting is difficult and requires expensive tooling. In addition, this glass rod must have a hole cut along the longitudinal axis of the rod cylinder. Again, this hole must be precisely cut. In addition, a cylindrically shaped glass rod is required.
Next, the two halves of the glass rod are coated along their outer circumference with a layer of metal. Next, a layer of zinc oxide (ZnO) is applied over the first layer of metal. Lastly, another layer of metal is applied over the zinc oxide over the entire periphery of the rod.
The layer of zinc oxide acts as a piezoelectric film and when a RF electrical source is applied to the metal layers, the zinc oxide produces acoustic waves. The acoustic waves may be focused through the glass material at the core of the fiber. As a result, the contents of the lights transmitted through the core of the optic fiber may be information modulated or interrogated.
The above arrangement requires that the glass rod be cylindrical in shape to provide precise coupling to the optic fiber core. Shapes of the transducer other than round are inoperable. In addition, the glass halve and longitudinal hole must be cut in the glass with a great deal of precision. These tasks are very difficult to perform and require very expensive equipment.
One such arrangement is shown in an article entitled Acoustooptic Modulators for Single-Mode Fibers, published by the Journal of Lightwave Technology, Vol. LT-5, No. 7, July, 1987.
Accordingly, it is an object of the present invention to provide an acoustooptic transducer arrangement for efficiently coupling to an in-place optic fiber which may be easily manufactured and attached to the optic fiber.